The present invention relates to a power transmission control device, a power transmission device, an electronic instrument, a non-contact power transmission system, and the like.
In recent years, non-contact power transmission (contactless power transmission) which utilizes electromagnetic induction to enable power transmission without metal-to-metal contact has attracted attention. As application examples of non-contact power transmission, charging a portable telephone, a household appliance (e.g., telephone handset), and the like has been proposed.
JP-A-2006-60909 discloses related-art non-contact power transmission. JP-A-2006-60909 implements data transmission from a power reception device (secondary side) to a power transmission device (primary side) by means of load modulation. The power transmission device determines whether the data transmitted from the power reception device is “0” or “1” by detecting an induced voltage in a primary coil using a comparator or the like.
According to the technology disclosed in JP-A-2006-60909, the data transmitted from the power reception device is detected by comparing the peak voltage of the induced voltage with a given threshold voltage. However, the threshold voltage used to determine the detected voltage varies due to a variation in an element constant such as a power supply voltage or coil inductance. This makes it difficult to accurately detect a change in secondary-side load.